Generative Expand Issues When you use Generative Expand, the output image will still have the same total resolution as the original. The difference is that now has to fit more of the scene into that same pixel budget. So the original subject (in this case, the face and details) ends up taking up a smaller portion of the frame, which is why things look a little softer compared to the original.
Think of it like zooming out on a photo: the image itself hasn't lost quality, but your subject is now smaller within the frame, so fine details are less visible.
A few things that can help:
After expanding, try using the Upscale tool it's designed exactly for this kind of situation.
You can also try expanding in smaller steps rather than one large jump, which tends to give better results.